Within recent years the number of electronic applications that employ optical devices has been rapidly increasing. Typically, optical fibers carry light signals that are coupled to a variety of optical devices, such as lasers, amplifiers, modulators, splitters, multiplexers/demultiplexers, routers, switches and receivers. As is well known, the use of optical fibers and devices leads to higher data through puts and increased communication channel bandwidths.
One drawback in employing optical fibers and optical devices is the need for reliable and accurate coupling between a fiber and an optical device. Typically, the diameter of a single mode fiber is approximately about 7 microns. The diameter of a waveguide employed in a semiconductor optical device is about 1.5 microns. Therefore, the coupling efficiency is small. One way to overcome coupling mismatch is to employ a fiber lens at the fiber end. Typically, a fiber lens is formed by etching the tip of the fiber end to define a convex shaped portion that acts as a lens. However, the process of forming a fiber lens is time consuming and requires an alignment accuracy in the order of 1/10th of micro resulting in a substantially costly optical coupling.
Another drawback in employing optical fibers and optical devices is optical index mismatching. Typically, the refractive index of a fiber material which is about 1.5, is different from the refractive index of a semiconductor optical device which is about 3.3. Therefore light traveling from a fiber to an optical device, or vice versa, experiences optical reflections. Conventional coupling systems employ anti-reflective coating material to provide a more suitable optical matching between the medium that light travels through. In the case of fiber to optical device coupling, because the optical fiber is made of glass, an air gap between the fiber end and the semiconductor surface is provided so that the fiber end would not damage the surface of the semiconductor optical device. Thus, the medium traveled by light comprises optical fiber to air and air to a semiconductor optical device. In order to alleviate reflection, it is necessary to treat the fiber end with an antireflective material that provides appropriate matching between glass and air. Furthermore, in order to alleviate reflection, between air and the semiconductor material, it is necessary to treat the semiconductor surface with an antireflective material that provides appropriate optical matching between air and the semiconductor. The process of treating antireflective materials on both optical fiber and semiconductor device is time consuming and leads to additional cost for coupling optical fibers to semiconductor optical devices.
Thus, there is a need for an improved coupling system that provides a reliable, accurate and expedient coupling between optical fibers and semiconductor optical devices.